Method of making miniature lamps



1959 H. WIEDENMANN METHOD OF MAKING MINIATURE LAMPS Filed June e,' 1956 Fig. 3

I VEN TOR HAN WIEDENMANN ATTORNEY United States Patent METHOD OF MAKING MINIATURE LAMPS Hans Wiedenmann, Heidenheim (Brenz), Germany, as-

signor to Patent-Treuhand-Gesellschaft fiir eleklrische Gliihlampen m.b.H., Munich, Germany Application June 6, 1956, Serial No. 589,783

Claims priority, application Germany June 16, 1955 6 Claims. (Cl. 316-20) The present invention relates to the manufacture of vacuum devices and relates more particularly to the method of exhausting and/or gas filling miniature or what may be termed subminiature incandescent or discharge lamps and the article produced thereby.

An important operation in the manufacture of vacuum devices such as incandescent lamps or the like includes the process of exhausting the bulb. This has been accomplished in various ways. A well known and common practice is to provide what is termed a stem which consists of a filament lead-in wires and an exhaust tube. The stem is sealed to the bulb neck and the bulb evacuated by means of the exhaust tube which is locally heated and tipped or pinched old. This method of what is known as a sealing-in and exhaust operation is satisfactory in the manufacture of the average size conventional lamp. In the case of miniature lamps or the like, however, and especially lamps of even smaller size for special use, the ordinary method of sealing-in and exhaust is not practical, owing to the dimensional limitations encountered.

In order to bring about a practical method to meet commercial demands, various methods have been proposed for the manufacture of miniature lamps, one of which was to seal the lead-in wires and exhaust tube directly in the bulb neck and, in order to hold open an exhaust passage, a copper wire was inserted therein and later removed; or the leading-in Wires were in the form of tubes through which the bulb was exhausted. It was also proposed to dispense with an exhaust tube and hold a mandrel to be sealed in the bulb neck after sealing oil or pinching, after which the mandrel was removed to leave an aperture for exhaust purposes; the opening being sealed by a plug of melted glass. gas filling being performed in a vacuum chamber.

The various methods as heretofore proposed and, which, under certain conditions may have met requirements to a limited degree, have been found unsatisfactory in meeting the present day demands for automatic and economic volume production. In cases where the operation must be performed in a vacuum chamber, difiiculties arise in holding the chambers gas tight and, since relatively large chambers are essential, gas losses to an appreciable degree cannot be avoided nor can be desired elfective results be attained as in the direct exhaust method.

The present invention provides an improved and practical method of manufacturing electric incandescent or glow discharge lamps of the small size or miniature type. The evacuation of small size lamps in accordance with the present method employs a metallic exhaust tube, which with filament supporting leading-in wires, is first sealed in a pinched or compressed glass portion of the bulb neck. The lamp is then exhausted and, if desired, gas filled; the compressed glass or press about the exhaust tube is then reheated, and during the heating to soften "the press, the exhaust tube is withdrawn. During the withdrawal of the exhaust tube, the softened glass is compressed to close the passage and hermetically seal the bulb.

The exhaust and 2,914,371 Patented Nov. 24, 1959 It is an object of the invention to provide a method of exhaust applicable to automatic equipment in the manufacture of extremely small size lamps.

Another object is to provide a method wherein a bulb is exhausted through an exhaust tube and the tube removed from the bulb.

Another object of the invention is to provide a method of exhausting a bulb by means or" an exhaust tube and in sealing the bulb during the removal of the tube.

Another object of the invention is to provide a method whereby a miniature lamp may be exhausted and hermetically sealed to provide a lamp bulb having a solid end wall or press of reduced proportions.

Other objects, advantages, and modifications will be evident to those skilled in the art to which the present invention appertains from the following description and the accompanying drawing in which:

Fig. 1 shows a cross sectional view of a lamp bulb and a vacuum bulb gripping member, the bulb being held above a lamp mount supported by gripping tongs, the mount being in position to be enclosed by the bulb;

Fig. 2 is a fragmentary top view of the mount support or gripping tongs;

Fig. 3 is a view of the parts shown in Fig. 1, with the bulb moved to enclose the mount and showing an exhaust tube disposed in the bulb neck with a pair of burners which serve as clamping jaws in position to heat the bulb neck;

Fig. 4 is a View similar to Fig. 3 with the jaws in clamping position;

Fig. 5 is a view similar to Fig. 4 showing the jaws retracted and burners operating to heat the bulb neck after an exhaust operation;

'Fig. 6 is a view similar to Fig. 5 showing the exhaust tube removed and the jaws in clamping relation to the bulb neck;

Pig. 7 shows an exhausted bulb ready to be based;

Fig. 8 is a view of a modification wherein additional burners are provided to direct flames below the bulb neck and the middle blade of the tongs being reduced in thickness and also shows in cross section the exhaust tube connected to the nozzle of a pump; and

Fig. 9 is a sectional view showing a double-way exhaust tube.

In the selected example of a practical embodiment of the invention as illustrated in the drawings, the apparatus for practicing the method is shown as applied to perform a sealing-in and exhaust operation in connection with what are herein termed submim'ature incandescent lamps. Lamps of these diminutive sizes find use in toys, various forms of surgical and scientific instruments, as well as certain limited industrial applications.

The drawings illustrate apparatus for practicing the method as applied to a lamp of the subminiature type which includes a glass bulb 9 to enclose a coil filament 19 connected to leading-in wires or conductors 11.

The leading-in wires are held by what is herein termed a holding tongs 12. The holding tongs or gripping memher as shown schematically in Fig. 2, consists of a fixed section or finger 13 intermediate movable jaw members or fingers 14 and 15 which are movable relative to section 13 by any suitable means as, for example, about pivots (not shown). The leading-in wires 11 are secured between jaws l4 and 15 and the intermediate section 13 to support the filament 10 in position to be enclosed by glass bulb 9. The leading-in wires and connected filament are pre-formed in accordance with common prac-v tice and may be considered as the mount element of the lamp.

The section 13 of the tongs 12 is provided with an aperture 16 to receive a metallic exhaust tube 17 one end 3 of which, when inserted through the aperture 16, will be disposed centrally between the leads 11.

A vacuum gripper member 19 of any suitable type known to the industry is employed to grip the bulb and position the neck portion 20 in axial alignment with the aperture and with the edge of the neck portion of the bulb in contact with the upper surface of the tongs 12. The exhaust tube 17 is held by suitable means (not shown) adjacent to the opposite surface of the tongs. The bulb is moved by means of the gripper member 19 and the bulb neck portion being in contact with the tongs, the tongs are moved downwardly as indicated by arrow X, Fig. 1, until the end portion of the exhaust tube is disposed in the bulb neck as shown in Fig. 3.

When the bulb neck and the exhaust tube are positioned as shown, the bulb neck is heated to soften the glass which is then compressed about the exhaust tube and the leading-in wires. This compressing operation is accomplished by providing a pair of clamping or presser jaws 21 and 22 actuated by any suitable means (not shown). Although separate fires may be provided to heat the bulb neck, it has been found advantageous to provide the jaws 21 and 22 with burners connected in the usual manner to a source of fuel supply (not shown).

The jaws are initially positioned in spaced relation to the bulb neck as shown in Fig. 3, and the burners are operated to heat the bulb neck to soften the glass to a predetermined degree. The flames are then extinguished and the jaws are moved to compress the glass about the exhaust tube and leading-in wires as shown in Fig. 4.

The lamp is then exhausted in the usual manner as well known in the art and, if desired, may be gas filled.

After the bulb has been exhausted, the jaws are moved from contact with the press as shown in Fig. 5, and the burners are operated to again heat the neck or press of the bulb. When the bulb neck has been heated to a selected degree, the tongs are moved to slowly lift the bulb relative to the exhaust tube, thereby withdrawing the exhaust tube. It has been found practical to especially direct the burner flames toward the exhaust tube, so as to heat said exhaust tube more intensely than the surrounding glass. The exhaust tube will then impart its heat to the glass and is easily withdrawn. As the exhaust tube is being withdrawn, the clamping jaws are moved to compress the glass and hermetically close the exhaust passage to form a solid body of glass about the leadingin wires as shown in Fig. 6. The lamp may then be lifted from the holding tongs by means of the vacuum gripper.

The bulb with the filament supported therein having now been exhausted is ready to be based. If the lamp is to be provided with contact pins in place of a base, the contact pins may be initially connected to the leads and embedded in the press or end wall during the clamping or pinching by the jaws.

Fig. 8 shows a modification wherein a pair of additional burners 26 and 27 are provided to supply added heat to the metal exhaust tube and fixed blade 28 which may be of thin refractory material so as to reduce the heat transfer rate to the press of the bulb 30. The exhaust tube is shown with an end disposed in a generally cone shaped member 31 in nozzle 32 of an exhaust machine, the cone shaped member being secured by screw cap 33. As will be evident, the attachment for the exhaust as shown including nozzle 32 may be employed to connect the exhaust tube to an exhaust machine when practicing the present method or the connection between the exhaust tube and the exhaust machine may be varied to meet conditions.

In accordance with the present method, an extremely small diameter and thin walled metallic exhaust tube may be employed. It has been found practical to use a tube having an outside diameter of about 2 mm. or less and a wall thickness of about 0.5 mm.; thereby making practical the commercial manufacture of extremely small size lamps as, for example, lamps having a maximum bulb diameter of about 5 mm. or less. The dimensions of the exhaust tube will in each case be determined by the dimensions of the lamp. It has been found preferable to make the exhaust tube of copper or heat resistant steel for the average size small lamps. In the manufacture of lamps of the smallest dimensions, the exhaust tube may be coated with glass, enamel, or borax, which have a lower melting point than the glass of the lamp, thus making the exhaust tube more easily removable at the second heating. If a suitable non-scaling material is used for the exhaust tube, it may be used repeatedly as desired.

In filling the lamps with gas also a double-way exhaust tube may be used, i.e. a tube as shown in Fig. 9 which is divided into two channels 34, 35 by a partition wall 36. In this case, the gas is blown through one of the channels 34 into the bulb, while the air and the surplus of the gas is able to escape through the second channel 35. Thus, for instance, flash light lamps containing a combustible material may be filled with oxygen without the necessity of a previous evacuation.

From the foregoing it will be evident that the present method will meet the requirements of high speed automatic lamp manufacture as applied to miniature lamps and especially to lamps of subminiature proportions.

What is claimed is:

1. The method of making miniature lamps filled with gas which comprises supporting a glass lamp bulb with a neck portion surrounding a leading-in conductor and a double-way exhaust tube providing two channels therein, heating to soften that neck portion, compressing the heated glass to seal the exhaust tube and conductor in an end wall of the bulb, blowing gas through one channel of the exhaust tube into the bulb, thereby driving out the air and the surplus of the gas through the other channel of the exhaust tube, heating said end wall of the bulb and exhaust tube again to soften said end wall, withdrawing said exhaust tube and compressing the softened end wall during the withdrawal of said tube, thereby removing the exhaust tube and its channels and hermetically sealing said lamp bulb.

2. The method of making miniature lamps which comprises supporting a glass lamp bulb with the neck portion surrounding a temporary exhaust tube providing an exhaust passage, heating to soften said neck portion, compressing the heated glass to temporarily seal the exhaust tube in a compressed glass body portion of the bulb to provide a temporary exhaust passage from the bulb by the exhaust passage of said exhaust tube, exhausting the bulb through said exhaust passage, heating to soften said glass body, withdrawing said exhaust tube in its entirety and compressing the softened body during the withdrawal of said tube, thereby removing the exhaust tube and its passage and hermetically sealing said lamp bulb.

3. The method of making miniature lamps which comprises supporting a glass lamp bulb with the neck portion surrounding a leading-in conductor and a temporary exhaust tube providing an exhaust passage, heating to soften said neck portion, compressing the heated glass to permanently seal said conductor in an end wall of the bulb and temporarily seal the exhaust tube in said wall to provide an exhaust passage from the bulb by the exhaust passage of said exhaust tube, exhausting the bulb through said exhaust passage, heating to soften said end wall, withdrawing said exhaust tube in its entirety and compressing the softened end wall during the withdrawal of said tube, thereby removing the exhaust tube and its passage and hermetically sealing said lamp bulb.

4. The method of making miniature lamps which comprises supporting a glass lamp bulb with the neck portion surrounding filament supporting leading-in wires, positioning one end of a temporary metallic exhaust tube within said neck portion thereby providing an exhaust passage through said tube from within said bulb to the exterior thereof, applying a source of heat to soften said neck portion, removing said heat source, compressing the softened neck portion about said metallic exhaust tube and leading-in wires, exhausting said bulb through the passage of said metallic exhaust tube, applying a source of heat to soften said compressed neck portion, withdrawing the metallic exhaust tube and applying pressure to said softened compressed neck portion during the withdrawal of said tube to hermetically seal said lamp.

5. The method of making miniature lamps which comprises supporting a glass lamp bulb having a maximum outside bulb diameter of about 5 mm. and positioned with the neck portion surrounding a temporary metallic exhaust tube having an outside diameter of about 2 mm. and a wall thickness of about 0.5 mm., heating to soften said neck portion, compressing the heated glass to temporarily seal the exhaust tube in a solid end wall formed from said neck portion of the bulb, exhausting the bulb through the metallic exhaust tube, heating to soften said end wall, withdrawing the metallic exhaust tube and compressing the softened end wall during the withdrawal of said tube to hermetically seal said lamp bulb.

6. The method of making miniature lamps which comprises supporting a glass lamp bulb having a maximum 6 outside bulb diameter of about 5 mm. and positioned with the neck portion surrounding filament supporting leading-in wires extending from said neck portion, disposing one end of an exhaust tubehaving an outside diameter of about 2 and a wall thickness of about 9.5 mm. within said neck portion, applying a source of heat to soften said neck portion, removing said heat source, compressing the softened neck portion about said exhaust tube and leading-in wires, exhausting said bulb through said exhaust tube, applying a source of heat to soften said compressed neck portion, withdrawing the exhaust tube in its entirety, and applying pressure to said softened compressed neck portion during the withdrawal of said tube to hermetically seal said lamp bulb.

References Cited in the file of this patent UNITED STATES PATENTS 709,996 McBerty Sept. 30, 1902 2,116,384 Cartun May 3, 1938 2,477,372 Herzog July 26, 1949 2,556,059 Braunsdorlf June 5, 1951 2,794,699 Eber June 4, 1957 

